Pinboard is a simple, functional bookmarking site, reminiscent of Delicious in its pre-Yahoo! prime, but it comes with a small catch. To join Pinboard, there's a one-time fee based on the number of users who have signed up so far. The fee is $0.001 times the number of users already signed up. As of a moment ago, it's a little over $4.50 to get an account. Instead of "social bookmarking," pinboard is "antisocial bookmarking," designed not too get too big and too diluted with spam as quickly as Delicious did.

You get some pretty good features in exchange for your fee. Pinboard includes a separate, lightweight "to read" option, for stuff you want to come back to, but don't want to share or put in your main list. You can import or export Delicious bookmarks, and, as Pinboard's developer notes in a little dig at Ma.gnolia, there are nightly backups, so the risk of data loss is minimal. If a better, more streamlined Delicious is your cup of tea, you should join Pinboard now, before it gets too expensive.

Any thoughts on the price at which new memberships start to level off?